Mu element-generated gene conversions in maize attenuate the dominant knotted phenotype

Area of Science:

• Plant genetics
• Molecular biology
• Developmental biology

Background:

• The knotted1 gene (Kn1) is crucial for leaf morphology, with dominant mutations like Kn1-O, caused by a tandem duplication, leading to altered leaf phenotypes.
• Mutator (Mu) insertions near the Kn1-O duplication junction can suppress these leaf phenotypes and promote recombination, generating derivative alleles.

Purpose of the Study:

• To investigate the genetic mechanisms underlying the generation of novel Kn1-O derivative alleles.
• To characterize the impact of specific DNA insertions on the knotted1 gene's phenotype and expression.

Main Methods:

• Analysis of Kn1-O derivative alleles with varying insertion lengths.
• Molecular characterization of inserted DNA sequences and their flanking regions.
• Phenotypic assessment of plants carrying the modified Kn1 alleles.

Main Results:

• Two new derivative alleles were identified, each retaining the tandem duplication but incorporating insertions of 1.7 kb and 3 kb.
• These insertions originated from sequences flanking the distal repeat unit of the original duplication.
• A 1.7-kb insertion partially dampened the knotted phenotype, while a 3-kb insertion completely suppressed it.

Conclusions:

• Gene conversion, likely triggered by double-strand breaks during Mu excision, is proposed as the mechanism for generating these derivative alleles.
• The size and location of insertions within the Kn1 tandem duplication significantly influence gene expression and phenotypic outcome.
• These findings provide insights into the dynamic nature of gene duplication and mutation in plant development.